Circumcising newborn boys increases their risk of cot death, new research suggests.

Male babies who have their foreskins removed are likely to suffer from the condition, also known as Sudden Infant Death Syndrome (SIDS), due to the stress of the procedure, a UK study found.

Such stress may include bleeding and pain or could be related to the procedure separating the infant from its mother and restraining it to a board.

Researchers believe this may explain why cot death is more common in baby boys than girls.

They wrote: ‘[Male circumcision], the most common unnecessary surgery in the world, is a major risk-factor for SIDS.’

Cot death kills around 300 babies in the UK and 3,500 every year in the US.

How the research was carried out

Researchers from the University of Sheffield analysed circumcision rates in babies born between 1999 and 2016 in 15 countries and more than 40 US states.

Prematurity data was also collected from the Center for Disease Prevention and Control, as well as the charity March of Dimes Foundation.

The findings were published in the journal bioRxiv.

Cot death is lower in populations who do not circumcise baby boys

Results further suggest SIDS rates are significantly lower in US states where Hispanic people make up more than eight per cent of the population. Spanish-speaking countries do not generally circumcise their boys.

In the 22 US states analysed where the health insurance Medicaid covers male circumcision, cot death is significantly higher.

Findings also imply babies born between 24 and 27 weeks, rather than full term at 40 weeks, are three times more likely to die from SIDS.

This may be due to the stress of being hospitalised in intensive care units, or their increased risk of bleeding or complications.

The researchers believe their results should encourage people to avoid male circumcision unless it is medically needed, such as if the foreskin is too tight or is recurrently becoming infected.

Such procedures should also be delayed until the child is at least seven years old, if possible.

The scientists add parents should be informed of circumcision’s SIDS risk.